The hydrocarbon exploration and recovery industry is forced with growing demand worldwide and therefore faced with the ever-increasing need for greater efficiency in completing boreholes for production both from cost and rapidity standpoints. In an effort to continue to raise the bar that represents these interests, inventors are constantly seeking out new ways to improve the process. While many improvements have been made and successfully implemented over the years, further improved procedures, configurations, etc. are still needed. In the downhole environment directly, multilateral wellbore construction and completion has become increasingly ubiquitous in recent years. Multilateral wellbores allow for a greater return on investment associated with drilling and completing a wellbore simply because more discrete areas/volumes of a subterranean hydrocarbon deposit (or deposits) is/are reachable through a single well. Moreover, such multilateral wellbore systems have a smaller footprint at the earths surface, reducing environmental concerns. Multilateral wellbores generally require “junctions” at intersection points where lateral boreholes meet a primary borehole or where lateral boreholes (acting then as sub primary boreholes) meet other lateral boreholes. “Junctions” as is familiar to one of skill in the art are “Y” type constructions utilized to create sealed flow paths at borehole intersections and are generally referred to as having a “primary leg” and a “lateral leg”.
There is a need in the industry for the flow of fluids at a multilateral intersection to be isolated from the formation. This is commonly known as a sealed junction. There are currently a number of ways of achieving this. For a given main well bore size two tubing strings can be run, one to the main bore and one to the lateral. If larger tubing strings are required then either a larger main bore is required or at least one of the tubing strings must be shaped prior to installation. An alternate to these is to construct the sealed junction downhole at the intersection of the main bore and lateral. Each of these methods has advantages and disadvantages. By utilizing two small tubes the junction can withstand high pressure differentials, but forgoes flow area and hence production rate. A large main bore and large tubing strings gains flow area and rate with moderate to high pressure ratings, but the increased sizes can have a major financial impact on numerous other related equipment in the overall well system. Junction systems where the tubing strings are not round end up with increases in flow area and rate over the small tubing strings, but are inherently lower in pressure and load rating. Systems where the sealing mechanism is assembled down hole have so far been complex to manufacture and install, with minimal increase in flow area, and with pressure ratings approximately equal to the non-round versions.
Since ease of installation, sealing and high overall strength characteristics are always a high priority, improved junction systems are always well received by the relevant art.